Heterochronic truncation of odontogenesis in theropod dinosaurs provides insight into the macroevolution of avian beaks.

ABSTRACT: Beaks are innovative structures characterizing numerous tetrapod lineages, including birds, but little is known about how developmental processes influenced the macroevolution of these important structures. Here we provide evidence of ontogenetic vestigialization of alveoli in two lineages of theropod dinosaurs and show that these are transitional phenotypes in the evolution of beaks. One of the smallest known caenagnathid oviraptorosaurs and a small specimen of the Early Cretaceous bird Sapeornis both possess shallow, empty vestiges of dentary alveoli. In both individuals, the system of vestiges connects via foramina with a dorsally closed canal homologous to alveoli. Similar morphologies are present in Limusaurus, a beaked theropod that becomes edentulous during ontogeny; a

SUBMITTER: Wang S 

PROVIDER: S-EPMC5642708 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature